Printing mechanism



y 4, 1944; A. w. MILLS 7 2,353,057

PRINTING MECHANISM Filed Ap ril a, 1941 INVENTOR ALBZKT 71 M/LZS ATTORNEY Patented July 4, 1944 PRINTING MECHANISM Albert w. Endloott, N. '21, assignor to In-=- ternational Business Machines Corporation, New York, N. Y., a corporation of New York Application April 8, 1941, Serial No. 387,435

4 Claims. (Cl. 101-93) This invention relates to printing mechanism and more particularly to the type of printing mechanism'in which a positionable type bar or element is struck by a hammer to efl'ect an impression on a record against a platen.

A particular object of the invention is to improve the operation of such printing hammer to prevent what is known as shadow" printing. Usually, the printing hammeris latched under spring tension and upon release strikes the type element, rebounds therefrom and under the infiuence of the actuating spring returns to strike the type a second time but with a lighter blow. Under ordinary circumstances, the actuating spring is generally not sufllciently strong to produce this second blow. Occasion arises, however, where the printing hammer is required to strike the type with greater impact as where printing is efiected upon multiple record sheets interleaved with the usual carbonsheets. The extra force is obtained by employing actuating springs of greater tension, so that the forces creating a double impression are then present.

In carrying out the objects of the invention, an interposing pendulum is pivoted on the type hammer and so arranged that, upon the initial rebound of the hammer from the typ the inertia of the pendulum swings the interposer into a position where it acts as a limiting stop, so that a further movement of the hammer in striking direction is halted before the hammer reaches the type a second time.

Other objects of the invention will be pointed out in the following description and claims and illustrated in the accompanying drawing, which discloses, by way of example, the principle of the invention and the best mode, which has been contemplated, of applying that principle.

In the drawing;

Fig. 1 is a view showing the printing hammer iii II. A spring l3 connected between the extension Iii and a fixed bar i9. is normally tensioned to swing the hammer, clockwise, when the extension i5 is released. When the type bar has been positioned, the latch i6 is rocked clockwise in the usual manner and spring l8 will rock the hammer I3 to its striking position which is shown in broken lines in Fig. 1. At such time, the usual restoring ball 20 is in its right hand position, as indicated in broken lines, out ofthe path of the hammer. On striking the type element ii, the lighttype spring 2i is compressed and printing is eiIected on the records interposed between the usual ribbon and the platen 12. The hammer then re-. bounds, causing spring i8 to become extended and in turn, the spring throws the hammer clockwise again with less force, of course, than originally.

For the purposes of the present invention, a pendulum 22 having a weighted extremity 23 and an interposin g arm 24 is pivoted by means of a stud 25 on the printing hammer. The weighted end 23 is shouldered as indicated by the line 26 (Figs. 2, and 3) so that, with the hammerin its latched position, the shoulder rests against the right hand edge of the hammer. When the hammer is released for initial impact, the pendulum is rocked therewith with'the'parts maintaining their relative relationship as indicated by the broken line. Extending across to the right of the hammer is a fixed bar 21 which the hammer approaches but does not actually contact when the hammer is tripped. This is the usual bar provided to receive the blow of the hammer if the.

normal conditions, the type element is generally and its actuating mechanism and its relationship to the type which it is to strike.

Fig. 2 is a view showing the printing hammer in another position.

Fig. 3 is an isometric view of the pendulum.

A form of printing mechanism to which the invention is applied is shown in my Patent 2,131,918, granted October 4, 1938. As explained in such patent, a reciprocal type bar designated I0 is positioned vertically to bring a selected type element ll into printing position opposite platen i2. In the plane of the type bar I0 is a printing hammer l3 freely pivoted on a fixed shaft it. The hammer is provided with a latching extension l5 which is normally engaged by a latch l5 pivoted on a rod 5 in position so that the bar 21 is not struck.

When the hammer rebounds from the type element ii, the inertia of the pendulum 22 causes a relative rotation between the bar and the pendulum to bring the parts into relative positions shown in Fig. 2, in which figure it will be seen that the interposing arm 24 of the pendulum is in position to strike against the fixed bar 21. In other words, the pivoted, weighted interposer 22 moves,

during hammer impact and rebound, so that the weight 23 of the interposer approaches the line of travel of its pivot 25. Motionof the hammer during rebound, gradually arrested and then reversely impelled, therefore, does not give the weight an equal, reverse acceleration away from the line of travel of the pivot, and the interposer, due to its inertia remains in the elevated position against the force of gravity during the rebound stroke. Thus, on the second stroke of the hammer its forward movement will be limited, due to the engagement of the interposer 24 with the bar 21, and the type hammer cannot strike the type element a second time. Later, the usual restoring bail 20 engages the hammer and forcibly rocks it back into its latched position preparatory to a further printing operation. It is thus seen that through the provision of a simple interposing pendulum, such as 22, the type hammer will only strike the type element once, regardless of the tension that may be applied to spring I8, and any bounce of the hammer will be restricted so that the type element is not afl'ected thereby.

While there has been shown and described and pointed out the fundamental novel features of the invention as appliedto a single modification, it will be understood that various omissions and substitutions and changes in the form and details of the device illustrated and in its operation may be made by those skilled in the art without departing from the spirit of the invention. It is the intention therefore to be limited only as indicated by the scope of the following claims.

What is claimed is:

1. In a printing machine having a pivoted printing hammer, a latch normally holding the hammer in retracted position, a spring urging the hammer in striking direction and a fixed stop approached by the hammer when released, the combination of a weighted interposer pivoted on the' hammer and arranged to move integrally therewith in striking direction, the inertia of the weighted portion of the interposer upon rebound of the hammer causing relative movement between it and the hammer to bring a part of the interposer into engaging relationship with the said stop so that the hammer is prevented from effecting repetition of its striking action.

2. In a printing machine, a printing hammer, a spring actuating the hammer to cause it to eflect a printing stroke, a fixed stop, said hammer moving to within a predetermined distance of said stop during its printing stroke, a weighted interposer carried-by the hammer, and movable thereon into position between the hammer and stop to restrict the stroke of the hammer, said interposer being mounted on the hammer to travel with it in a predetermined relationship during a printing stroke, the mounting being such that inertia of the interposer upon reverse movement of the hammer will cause the interposer to move into restricting position.

3. In a printing machine, a pivoted hammer movable to printing position against a type element and movable out of printing position under rebound, a weighted member freely pivoted on the hammer and relatively movable thereon, a stop element, said member being engaged by and moving with said hammer during the latters movement to printing position and moving relatively to the hammer during the hammers movement out of printing position under the influence of the inertia of its weighting, said last movement bringing the member in cooperative relationship with the stop element to prevent subsequent movement of the hammer into printing position.

4. In a printing machine, a type carrier, printing hammer, a member pivoted on the hammer and having a'weighted extension normally tending to cause rotation of the member and serving to engage the hammer to establish a normal relationship therewith, a fixed stop, said ALBERT W. LHLLS. 

